Bradykinin-evoked acetylcholine release via inositol trisphosphate-dependent elevation in free calcium in neuroblastoma x glioma hybrid NG108-15 cells.
The mechanism underlying the bradykinin (BK)-induced increase of acetylcholine (ACh) release was studied in neuroblastoma x glioma hybrid NG108-15 cells and their synapses formed onto mouse muscle cells. External application of BK or iontophoretic injection of extrinsic inositol 1,4,5-trisphosphate (InsP3) into the cytoplasm of NG108-15 cells produced membrane hyperpolarization in the hybrid cells and an increase in the frequency of miniature end-plate potentials (MEPPs) in paired myotubes. Ba2+ blocked the hyperpolarization in response to BK, but facilitation of MEPPs was still observed. InsP3-dependent facilitation of MEPPs was also observed in cells where the InsP3 injections produced no detectable hyperpolarization or even depolarization. Real-time quantitative monitoring of intracellular free Ca2+ concentration [( Ca2+]i) with fura-2 in single NG108-15 cells showed that BK application or InsP3 injection induced an elevation of [Ca2+]i which coincided in time with membrane hyperpolarization recorded from the same cell. The [Ca2+]i rise produced by InsP3 injection started from the single site of injection and that produced by BK began from a deep compartment of the cytoplasm of the NG108-15 cells. The BK- and InsP3-evoked facilitation of MEPPs and the [Ca2+]i rise were relatively independent of extracellular Ca2+. These findings suggest that the BK-induced ACh release results not from membrane potential changes but from a transient InsP3-dependent elevation of [Ca2+]i.
Ogura
A
A
Department of Neuroscience, Mitsubishi Kasei Institute of Life Sciences, Machida, Japan.
Myojo
Y
Y
Higashida
H
H
D000109:Acetylcholine / Q000378:metabolism*; D000818:Animals; D001464:Barium / Q000494:pharmacology; D001920:Bradykinin / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D005071:Evoked Potentials / Q000187:drug effects; D005910:Glioma; D006822:Hybrid Cells / Q000187:drug effects / Q000378:metabolism*; D015544:Inositol 1,4,5-Trisphosphate / Q000494:pharmacology*; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D009447:Neuroblastoma; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology; D051381:Rats; D013569:Synapses / Q000187:drug effects / Q000502:physiology
D001464:Barium; D015240:Phorbol 12,13-Dibutyrate; D015544:Inositol 1,4,5-Trisphosphate; D000109:Acetylcholine; D001920:Bradykinin; D002118:Calcium